You need to install the NT client agent on each of the workstations you want to back up. There are no licensing restrictions on how many times you can do this.
Then at the server, start a backup job and open the client agents option. Right click Windows NT agents and select add using Auto Discovery. The workstations that you have installed the agent how should now appear. If not, make sure you have started the Client service on the workstations and try again.
Hope this helps.